Photographic paper.



Y.V SCHWARTZ.I

PHOTOGRAPHIC PAPER. APPLICATION FILED NOV. 12, 1906.

916,616. Fatented Mar. so, 1909.-

Yoan` SCHWARTZ., or HANOVER, GERMANY.

, Pnefroennrnro yarns;

Specification of Letters Patent.

meent-ed Meren so, ieoof Application led November 12, 1,90 Serial No. 343,034.

To'cll 'whom it may concerns .YBe-it known that l, YORK SCHWARTZ, a

subject of thKing of Prussia, German Ernperor, 'and resident vof 3 Eden street, Hanover, in the'German Empire, have invented an lrn roved Photographic Paper, ofl which the following is Van exact specification.

My` invention relates to the production of an improved paper for photographicpurposes.v

lt is a well knownfact that most kinds dinfaristoor the like emulsion.

lof paper 'contain largequantities ol"l metallic.y

particles o1' particles of other reducing substances, whereby such papers are rendered l perfectly useless for the production of photogra hic silver emulsion aper', more'- especia y, if emulsions, suci for instance as emu sions for copying out purposes, containing a surplus of soluble'salts of silver, come into consideration. Furthermore it is well known that few factories are in a position to produce a paper of 'the necessary qualities which` requires special experience for its.

'manufacture and its cost isvery considerable.

lt will'be readily understood that these .reducing impurities are rendered harmless, if a protecting layer is placed between the paper and the emulsion, which' rotecting layer prevents the impuritiesof t e aper and the soluble silver salts ofthe em ,sion from reacting one upon the other. A protecting layer having lWaterand alcohol-proof prop -g erties could be used, whereby a mere niechanical separation of. the emulsionand paper is obtalned. For reasons which cannot further be discussed here such attempts have failed silver emulsion layer.

to give av'satisfactory result. n

Now 'I have found that a good result can be obtained by coating the impure paper witha rotecting layer which contains salts insolub e or practically insoluble in water and alcohol. These latter salts react upon the silver salts 'diffusing from the emulsion in'to the aper film in such manner,A that insoluble si ver salts remaining yvithin the protecting layer are formed. A proper selection of the kind and the quantity 'of the compound distributed in the. protecting layer prevents all the, silver salt from getting to the aper and inversely no substance having 'a Dad effect upon the quality of the emulsion can enter. from the protecting layer into the tion an have a pure White color. In practice the protecting layer at the same time shall be substituted for the white layer for instance of 'baryta as usual in photographic emulsion papers, so that the paper provided with the protecting' layer can without an i further operation be coated with,the celloi'.-

The neutral phosphates of the earths, al-- kaline earths and of zinc, and among these particularly the neutral phosphate of cal- Ieiuni, are most suited forthe end in view. It may here be'pointed out that triand diphosphates 'of calcium, for instance the fcalciuni phosphoricuni, referred to'in the Deutschen Arznezbuch IV are excellently suitable for. the purpose intended.

The phosphate is' mixed with a binding means of'a sutliciently inactive and resistible character and then applied' to the raw paper as usual. onstrated that a perfect protection is obtained, if for instancev the coating contains about 40 grains of the .calciuni phosphoricurn referred to for each square'meter of the paper. The rotectin layer, of course,- can if desired,I le mixe( with additions, coloring matters or the like which are inactive and promote 'the durability of the finished emulsion paper.

'lo make my invention more clear, reference is had to the' accompanying drawing, in .'fhich:

ll1 igure 1 represents in a cross section and1 in an exaggerated scale the paper prepared according to my invention, Fig. 2 illustrates in a cross section the paper provided with a duction of a silver-emulsion paper, consisting yota paper-film, and a protecting layer placed on the paper film, the essential constituents of which layer are salts insoluble in alcohol and' water, uhich salts react upon 'the silversalts diffusing from the emulsion into the round in such manner that an insoluble si ver salt, remaining within the protecting layer; is formed.

2. The .he-reindescribed paper for the production of silver-snuilson paper, consisting of apaper-lihn, and a protecting layer placed on the paper ilni and containing essentially the phosphates of the earths. y

Experiments have deni- 3. The hereindescribcd paper for the production of a silver emulsion paper, consistin of a. oper-film, and a. rotecting layer place on t e. paper-film, an containing essentialhr the phosphates of the alkaline earths.

4. The hereindescrihed paper for the production of a lsilver-e1uulsion-paper, consisting of a paper-film, and a protecting layer, which is placed on the paper lm, and consists of salts insoluble in water and alcohol, together with inactive substances.

5. The hereindescribed paper-for the production of a silver-emulsion paper, consist mg of a paper-film, and .a protecting layer, which latter is placed on the paper-film and consists of salts insoluhlcin water and alcoh ol, and coloring material mixed therein.

6. The hereindescrihed paper for the pro- @mais duction of a silver-emulsion paper, consist ing of a paper-film and a protecting layer 2o pla-ced on the paper-lin and formedv of the phosphates of the earths and of inactive substances.

7. The hereindescribed paper for the production of a silver-emulsion paper, consistingof a paper-film, and a protecting layer pla-ced on the paper iilni, and formed of the phosphates of the alkaline earths and of coloring nuit-ters.

ln wit-ness whereof I have hereunto set my 30 

